Toroidal reactor designs as a function of aspect ratio

This paper presents a 'common basis' systems study of superconducting (SC) and normal-conducting (NC) DT-burning fusion power and materials testing reactor designs. Figures-of-merit for power and materials-testing reactors are respectively; projected cost-of-electricity (COE) and direct cost (DC). A common 0-D plasma modeling basis is used and the plasma geometry and engineering aspects of the SC and NC designs are treated in an equivalent manner that is consistent with the limitations of their respective magnet technologies and other design constraints. Aspect ratios A in the range 1.2≤A≤6 and plasma elongations in the range 1≤κ≤3 are explored and a MHD stability (beta limit) physics basis that accurately describes the increase of normalized beta βN and toroidal beta βT with a decreasing A and/or increasing κ is incorporated. With this MHD basis taken into account and with the usual reactor geometry, physics and engineering constraints and costing bases applied, the results of the study show that for power reactors the minimum COE is pointing towards lower A∼2 than generally found in previous studies. The minimum is broader with higher κ. For test reactors with similar fusion power output, the direct cost for NC options is significantly lower than for SC coil options. With the NC category, testing designs that combine intermediate A and higher elongation show promise as a D-T burn next step device that could provide scientific and testing data to support future SC and NC reactors. For example, a NC coil design with A∼2, κ=3 could produce 200 MW fusion power at 1.23MW/m2 average neutron wall loading at a total direct cost of about $643 M. This NC design with a fissile blanket could also convert ∼1270kg of fission reactor waste per full power year. (author)